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Questions and Answers
Which of the following describes gums?
Mucilages are soluble in alcohol.
False
What type of color does hydrolysable tannins produce when reacted with FeCl3?
Bluish black color
Tannins have an astringent effect in the ______.
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Match the following types of tannins with their characteristics:
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Which of the following is NOT a use of tannins?
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Essential oils are liquid mixtures that usually have no odor.
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Name a common example of a gum.
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Which of the following is NOT a property of volatile oils?
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Fixed oils can form soap upon hydrolysis.
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What type of oils are generally used as flavoring agents and in perfumery?
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The presence of ___________ determines the persistence of the stain on filter paper for fixed oils.
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Match the following oils with their characteristics:
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Which of the following statements about the detection of oils is correct?
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Condensed tannins are also known as hydrolyzable tannins.
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Volatile oils are often extracted from ___________ plants.
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Which of the following is NOT a primary metabolite?
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Fixed oils and fats are used primarily as binders in tablet formulations.
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What is the special chemical test for starch?
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Primary metabolites are found in all plants and have __________ value.
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Match the following primary metabolites with their uses:
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Which statement correctly describes secondary metabolites?
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Gums and mucilages are categorized as primary metabolites.
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Name one use of proteins in pharmacognosy.
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Study Notes
Chemistry of Crude Drugs
- Food storage products are primary metabolites found in all plants.
- Primary metabolites have nutritional value and can be used in pharmacy.
- By-products of metabolism are secondary metabolites that have specific functions, are important in pharmacognosy, and have a wide range of uses.
- Primary and secondary metabolites can be classified based on their chemical properties and uses.
Primary Metabolites
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Starch:
- A polysaccharide composed of glucose units.
- It is found in roots, rhizomes, and seeds as granules.
- Gives a blue color with iodine.
- Used as a diluent and binder in tablet formulation, a skin emollient, a dusting powder for cosmetics, and as an antidote for iodine poisoning.
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Proteins:
- Complex nitrogenous organic substances found as aleurone grains in seeds.
- Composed of amino acids.
- Gives a red color with Millon's reagent and a yellow color with picric acid.
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Fixed Oils & Fats:
- Esters of long chain fatty acids.
- Found in seeds, such as nutmeg.
- Can be detected with Sudan III.
- Used nutritionally, as solvents in intramuscular injections, for the preparation of soaps and plasters, and as laxatives, demulcents, and emollients.
Secondary Metabolites
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Gums and Mucilages:
- Polysaccharides or salts of polysaccharides.
- Gums are viscous secretions from trees that harden on drying and are soluble in water.
- Mucilages are insoluble in alcohol and form viscous colloids in water.
- Examples include gum acacia and psyllium.
- Detected with Ruthenium red or methylene blue.
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Tannins:
- Water-soluble polyphenolic compounds with high molecular weight that are widely distributed in the plant kingdom.
- Divided into two main groups: Hydrolysable tannins and Condensed tannins.
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Hydrolysable tannins (pyrogallol tannins):
- Give a bluish black color with FeCl3.
- Do not precipitate with bromine water.
- Upon heating with hydrochloric or sulfuric acids, they yield gallic or ellagic acids.
- Examples include those found in cloves.
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Condensed tannins (catechol tannins):
- Give a green color with FeCl3.
- Precipitate with bromine water.
- Decompose into red insoluble plobabhene and produce a red color in the drugs.
- Examples include those found in cinnamon and tea.
- Used as astringents for the digestive tract (treating diarrhea), antioxidants (anti-cancer, anti-ulcer properties), hemostatics for skin cuts, and in the manufacture of dyes and ink and the tanning of leather.
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Volatile Oils (Essential or Ethereal Oils):
- Odoriferous principles in plants composed of a mixture of hydrocarbons and oxygenated hydrocarbons.
- Secreted by specialized structures such as cells, glands, ducts, and hairs.
- Give a red color with Sudan III.
- Used for flavoring agents, in perfumery (lavender oil, rose oil), spices (clove), as carminatives (oil of anise), and have therapeutic uses such as urinary tract antiseptics and anti-rheumatics.
Comparing Important Concepts
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Starch and Protein:
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Chemical composition:
- Starch: polysaccharide of glucose units
- Protein: complex nitrogenous organic substances composed of amino acids.
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Occurrence:
- Starch: granules in roots, rhizomes, and seeds
- Protein: aleurone grains in seeds.
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Tests:
- Starch: blue color with iodine.
- Protein: red color with Millon's reagent and a yellow color with picric acid.
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Chemical composition:
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Hydrolysable Tannins (pyrogallol tannins) and Condensed Tannins (catechol tannins):
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Chemical composition:
- Both: water-soluble polyphenolic compounds with high molecular weight.
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Tests:
- Hydrolysable tannins: bluish black color with FeCl3, no precipitate with bromine water, yields gallic or ellagic acids upon heating.
- Condensed tannins: green color with FeCl3, precipitation with bromine water, decomposes into red insoluble plobabhene.
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Chemical composition:
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Description
This quiz explores the chemistry of crude drugs, focusing on primary and secondary metabolites. Learn about essential compounds such as starch, proteins, and fixed oils, and their uses in both nutrition and pharmacy. Test your knowledge of their properties and classifications.
